And for Theodora of Greece I think her father and the girl herself won't want the princess to convert into the roman catholicism.

As other poster said I think Constantine would be ecstatic to have a reigning Grand Duke for son-in-law, and he didn't have any problem with his sister converting to catholicism. Guillaume would never convert to her religion the same way they wouldn't move to Greece, he is not a regular person who can decide this things. I don't think most royals (I'm talking royal-borns now) would have a problem converting for their new country, because they've been taught since their births that it's their duty. For example, I suppose George I converted when he became King of Greece.

Probably, Luxembourg is the only country with a ruling Ducal family. There's a great chance that they'll get a good media coverage in Europe but not so much in the US unless he marries an American. Besides that all it might get is a small mention in the magazines and the news.

I work at bookstore and I have to put Majesty magazine back quite often. So if his eventual wedding ends up in thereit'll be all over america.

__________________"Zydrate comes in a little glass vile. And the vile goes into the gun just like a battery. And then the gun gets placed somewhere along your anatomy." Graverobber from Repo! The Genetic Opera

The paris hilton part made me have to check it out. That's hillarious. I hadn't thought about Princess Elisabeth von Thurn und Taxis with guillaume. She is worth more than he is but they could be a good couple and their children would be stunning.

__________________"Zydrate comes in a little glass vile. And the vile goes into the gun just like a battery. And then the gun gets placed somewhere along your anatomy." Graverobber from Repo! The Genetic Opera

So what are the qualifications to be Guillaume's wife? Do you think he will or can marry a commoner? I would like to see him marry someone of a different nationality maybe American because I am American and we haven't had a royal bride since Grace Kelly :( And now that William is out...we're over due

The head of the house (reigning Grand Duke/Duchess or regent) grants consent and then informs the Chamber of Deputies of his/her decision.

Although the decision rests fully with Henri, I suspect that he would discuss the marriage of his heir with members of his government/advisors before making his final decision. I'm sure if he had any reason to doubt the character or ability of the young woman in question he would seek the opinion of his government (particurally in the case of Guillaume not necessarily so in the case of "lesser" members).

I found relevant decree concerning the titles of Mlle. Maria Teresa Mestre and Mlle. Sibilla Weiller but no decree of consent. I also found naturalisation records for Princess Josephine-Charlotte and Mlle. Sibilla Weiller but not Maria Teresa. I couldn't find any sort of consent decree that would require counter signature by a member of the government for anyone. This goes along with my reading of the relevant documents that imply the head of the house grants his consent and informs the government. Theoretically speaking, the government plays no role in the approval/rejection of a potional spouse. Realistically, I have no doubt that the government could impress upon Henri their lack of interest in having a woman of a certain background become their HGDss.